1. Field of the Invention
The present invention relates to a reciprocating type compressor. More particularly, it pertains to a flow restricting structure in pressure passages between chambers in a reciprocating type compressor, which employs a drive plate to compress refrigerant gas.
1. Description of the Prior Art
In a compressor having a drive plate such as a swingable swash plate, the drive plate is mounted on a rotatable shaft inside a crank chamber. The rotation of the shaft is converted to reciprocating movement of pistons in associated cylinder bores by the drive plate. The refrigerant gas, supplied to the cylinder bores from a suction chamber, is compressed by the reciprocating movement of the pistons and then discharged from the compressor via a discharge chamber. Since the crank chamber is defined in a tightly sealed space, it is necessary to maintain the pressure of the chamber within a proper range.
However, leakage, or blow-by of compressed gas occurs between the outer cylindrical surface of the pistons and the inner cylindrical surface of the respective cylinder bores. The blow-by enters the crank chamber and raises the pressure within. Furthermore, in a variable type compressor, which automatically adjusts an inclining angle of the drive plate, the discharge volume of the compressor is changed by automatically adjusting the pressure inside the crank chamber according to a cooling load. Accordingly, compressors having a structure which discharges the pressure within the crank chamber into other chambers have been proposed. These compressors communicate the crank chamber with the discharge chamber or suction chamber for releasing the pressure.
Japanese Examined Patent Publication 3-55675 discloses such a compressor. In this compressor, a gas bleeding passage is formed between the suction chamber and the crank chamber. Blow-by gas from the compressing chambers of the cylinder bores, is returned to the suction chamber via the passage. This prevents excessive pressurizing of the crank chamber caused by the blow-by gas.
In addition, an air intake passage, provided with a release valve, is formed between the discharge chamber and the crank chamber. The valve has a valve control mechanism on which the pressure of the crank chamber acts by way of a pressurizing passage. The opening and closing of the valve is controlled by the mechanism according to the pressure within the crank chamber. The opening and closing of the valve adjusts the pressure inside the crank chamber. This alters the inclining angle of the swing swash plate and controls the discharge volume of the compressed gas.
In the above compressor, a restricting section is normally provided in a gas bleeding passage to regulate the flow of refrigerant gas to a predetermined amount before the gas is returned to the suction chamber. As shown in FIG. 12, the restricting section comprises through holes 105, 106 and a passageway 108. The holes 105, 106 are respectively formed in a cylinder block 103 and valve plate 104. The passageway 108 is grooved in the inner end face of a rear housing 107 to communicate the through hole 106 with a suction chamber 100. The width and depth of the passageway 108 function to restrict the amount of fluid flow. The passageway 108 may be formed in the end face of the cylinder block 103 instead of the rear housing 107.
However, employing the passageway 108, formed in the rear housing 107 or cylinder block 103, to serve as the restricting section of the bleeding passage 102 leads to certain problems. Namely, the passageway 108 is formed during the molding of the rear housing 107 or cylinder block 103 in the end face. The end face of the housing 107 or cylinder block 103 is then ground to make it smooth. However, the depth of the grinding changes depending on the molding condition of the end face. Thus, inconsistent grinding depth of the end face alters the depth of the passageway 108. As a result, the size of the passageway differs in each compressor. Therefore, performance may vary slightly between products.
To solve this problem, the passageway 108 may be machined to a predetermined depth from the end face after the end face of the rear housing 107 or cylinder block 103 is ground. However, such machining operations are complicated and troublesome.